The story begins with Yasuko Kurohime, a 28-year-old woman working a grueling job at a black company, struggling to repay her student loans. Her only solace is Mashiro, a stray white cat she cares for despite her cat allergy. One day, Mashiro runs into the road and Yasuko, in a desperate attempt to save her, is hit by a truck and dies.
She awakens to find herself in an afterlife-like space with a winged, lower-ranking goddess. The goddess explains that Yasuko has died and offers her reincarnation into another world with cheat abilities, as requested by a "great being" who pitied her. Yasuko, having no attachments to her bleak life, agrees, but her only wish is to be reunited with Mashiro. To her surprise, Mashiro is also present, having died in the same accident. The goddess grants Yasuko's wish, allowing her to bring Mashiro to the new world, along with a healthy body free of her cat allergy and other essential skills like language proficiency.
However, upon arrival, Yasuko discovers she has been reincarnated not as an adult, but as a five-year-old child. She also finds herself caught up in a "Saint Summoning" ritual, intended to bring a holy woman to this world to combat a growing miasma. The summoner, Prince Bakudekanto of the Geeta-Niiga Kingdom, is disgusted by Yasuko's infant form and abandons her in the dangerous "Abyss Wood" forest, deeming the summoning invalid.
Left alone and vulnerable, Yasuko's only companion is Mashiro. She soon discovers that Mashiro is no ordinary cat but the powerful cat god Bastet, who had previously been reincarnated as a kitten and cared for by Yasuko in her past life. Mashiro possesses incredible strength and skills, capable of defeating monsters with ease. When Mashiro defeats monsters, Yasuko inexplicably gains experience points, rapidly leveling up her own abilities, including her Saint skills (barrier, healing, purification) and gaining new ones.
Yasuko and Mashiro navigate the Abyss Wood, with Mashiro guiding them through traps and defeating monsters. They encounter the ghost of Manami Sakudaira, a former Saint who was also summoned and abandoned in this world centuries ago. Manami, a hikikomori who suffered bullying in her previous life, gifts Yasuko her "Trick Bag," a cheat item containing various useful skills like an item box capable of retrieving Earth items, a shape-shifting ability, and a pocket dimension with a building inside. Manami also transfers her Saint skills to Yasuko, significantly boosting their levels.
Yasuko, now equipped with powerful skills and an incredibly strong divine companion, sets out to escape the forest. She uses her enhanced Saint skills to purify the miasma and her barrier to protect herself. Mashiro's combat prowess and skills, like "Cat's Whiskers" for navigation and "Flying Claws" for offense, prove invaluable. Yasuko also gains new abilities through Mashiro's "Nekobaba" skill, which allows her to steal abilities from defeated monsters.
Their journey leads them to a dungeon where they encounter a powerful Death Bear. Mashiro defeats it, further increasing Yasuko's level. They then find a hidden chamber containing Manami's remains and her spirit. Manami, grateful for Yasuko's kindness, bestows her remaining Saint power upon Yasuko, maxing out her Saint skills. Yasuko, in turn, decides to take Manami's body with her, hoping to one day return it to her homeland.
Emerging from the dungeon, Yasuko and Mashiro face the challenges of the Abyss Wood. Yasuko's Saint skills, particularly her level 10 barrier and purification, prove effective against the poisonous miasma and powerful monsters. Mashiro continues to be Yasuko's formidable protector, defeating monsters like a Queen Bee and a Black Boar, which further boosts Yasuko's level and grants her new abilities.
During their travels, they hear a woman's scream. While Mashiro initially prioritizes safety and avoiding danger, Yasuko, empowered by her Saint abilities and a sense of justice, decides to investigate and help. She believes she cannot stand by when she has the power to assist others. Mashiro, though reluctant, follows Yasuko. They arrive to find a female knight, Amelia White Knight, and her knights overwhelmed by a pack of Black Boars. Yasuko's powerful barrier effortlessly defeats the monsters, astonishing Amelia and her men. Mashiro then swiftly dispatches the remaining boars, solidifying Yasuko's growing strength and her reliance on her divine companion.
